✅ Heat treated tool steel 6150 - Rockwell hardness 50-52 ✅ Aerospace grade #2024 Aluminum piston ✅ Mechanically locked piston driver interface ✅ This part is compatible with Hitachi ✅ NV90AG Coil Nailer | NV90AGSM 3-1/2 Inch Coil Framing Nailer | NV90AG(S) Nailer